My baby boy has an undescended testicle. What does this mean?

Some baby boys are born with just one testicle in the skin sac, or scrotum, that lies behind their penis. Usually, the other testicle is present, but it is higher up than it should be, in your baby's tummy. In a few children, this happens to both testicles. Whether one testicle or both testicles are undescended, the medical term is cryptorchidism.

Undescended testicles are common. In the UK, about one newborn boy in every 20 has at least one undescended testicle (Acerini et al 2009, GOSH 2012, NHS 2015). They are more common in babies who are born prematurely (Sumfest 2016).

Checking for an undescended testicle should be part of your newborn baby's routine checks (NHS 2015, PHE 2016). The newborn checks are carried out by a paediatrician or a specially trained midwife. Your doctor or midwife will have a look and feel to find out whether both your baby's testicles are in his scrotum (Tekgül et al 2010).

It's likely your baby's testicle will come down on its own before he's six months (Newson 2015). For this reason, doctors usually wait to start treatment. However, if your baby's testicle has not descended by six months, your doctor is likely to recommend treatment (Hutson 2010, Newson 2015, NHS 2015).

What is the treatment for an undescended testicle?

If your baby's testicle has not descended by the time he is six months old, your doctor will probably recommend a surgical operation called an orchidopexy. This is usually carried out when your child is between six months and two years old, ideally before he is one year old (Newson 2015, NHS 2015).

Your child will be asleep for the operation, under a general anaesthetic. The surgeon will look for the testicle, and bring it down into its place in the scrotum. If the testicle is quite high in your son's tummy, he may need to have the surgery in stages, with two operations about six months apart (GOSH 2012, NHS 2015).

On rare occasions, your son's surgeon may find that the testicle has not formed properly or is damaged. If so, she will remove the damaged testicle and may also secure the healthy testicle in your son's scrotum so it can develop normally (GOSH 2012).

In some children, the testicle goes back up again after surgery, so your son should have check-ups from time to time (Sumfest 2016).

What causes an undescended testicle?

In most baby boys, the testicles move down a passage from the tummy into the scrotum after 28 weeks of pregnancy (GOSH 2012, Sumfest 2016, Virtanen and Toppari 2008). An undescended testicle has not made or completed the journey to the scrotum. It has stayed in the tummy or only reached as far as the groin.

This is one reason why undescended testicles are more common in premature babies. These babies are simply born before the testicles have had time to complete their journey.

Generally, though, no one knows for sure what the cause is. It could be that smoking or drinking alcohol during pregnancy has an effect on the testicles, but these are only theories (Bathold 2008, Main 2009).

It's also possible that exposure to something in the environment, such as chemicals, is the cause. Again, the evidence is not complete. Part of the reason may be genetic, that is, babies inherit it from their parents (Barthold 2008, Main 2009).

Sometimes, an undescended testicle occurs along with other medical problems, such as a small opening in the tummy muscle wall, called a hernia (Virtanen and Toppari 2008). A hernia usually looks like a small lump on your baby's tummy or groin.

Will my son have problems in the future because of an undescended testicle?

Corrective treatment as a baby will help to protect your son's long-term health.

Having the operation while he's young can reduce his risk of testicular cancer in adulthood (Sumfest 2016, Walsh 2007).

Men with testicles that are left undescended have a higher risk of testicular cancer (GOSH 2012, Zhao Lin Lip et al 2013). Doctors can't agree on the exact reason for this, but one reason is that it's easier to check a descended testicle for lumps (Sumfest 2016).

Having treatment for undescended testicles in babyhood improves fertility in the long run (NHS 2015). Sperm need to be kept cooler than body temperature, so the normal position of the testicles below the body in the scrotum is ideal. An undescended testicle, situated in the tummy, for example, will be at normal body temperature – this slight increase in temperature may lower a man's sperm count (GOSH 2012).

If your baby's undescended testicle had to be removed during the operation because it was damaged, it shouldn't reduce his fertility in the long run (Sumfest 2016). Many men with one testicle become fathers (Sumfest 2016). In adulthood, your son should enjoy a normal sex life, but it's worth being aware that he may be self-conscious about how his genitals look when he reaches puberty. If you think your son would benefit from counselling at any point, start with a visit to your GP.

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